A new tumor-associated antigen, called Tennessee antigen (TAG), has been isolated from 95% of 154 primary human gastrointestinal tumors. In 208 patients with colorectal carcinoma, 81% showed elevated levels of TAG in their serum. In this proposal, TAG will be isolated from extract of adenocarcinoma of human gastrointestinal tract. Monoclonal antibodies (MoAb) against TAG will be produced. Spleen cells from Balb/c mice immunized with TAG will be used to fuse with Sp 2/0-Ag 14 cells by means of 30% polyethylene glycol to produce hybridomas. Culture fluids from hybridomas will be screened for antibodies by enzyme immunoassay. After identifying the cultures producing specific antibodies, the hybridoma cells will be grown and cloned by limiting dilution in fluid phase. Lines producing MoAb will be injected into Balb/c mice to produce MoAb-containing ascites fluid. The MoAb will facilitate analysis of structure and genetic origin of TAG. It can be used as part of a panel of MoAb to immunologically type the antigenic expression of colorectal carcinomas. Commercially, MoAb can be used for developing a sensitive radioimmunoassay for diagnosis of colorectal carcinomas. It may be useful in the treatment of human colorectal carcinomas. (2)